Medical devices comprising a therapeutic agent have been successful in treating the body tissue of a patient. For example, intravascular stents that have a coating containing, a therapeutic agent for preventing restenosis have been successful in reducing incidents of restenosis. In certain instances, in order to improve the reduction of restenosis, it may be desirable to increase the amount of the therapeutic agent that is delivered from the coating to the body tissue.
One way of increasing the amount of therapeutic agent that is delivered to the body tissue is to increase the amount of the therapeutic agent that is loaded into the coating. However, there are difficulties associated with coatings that contain large amounts of a therapeutic agent, such as controlling the release of the therapeutic agent. Particularly, larger amounts of therapeutic agents in the coating can be released too rapidly from the coating, thereby creating a “burst” effect instead of a desired sustained release of the therapeutic agent.
Another way of increasing the amount of therapeutic agent that is included in a medical device coating and delivered to the body tissue is to increase the surface area of the coating that is exposed to the tissue. In general, when a coating composition is disposed on the surface of a medical device, such as a stent, the exposed surface area of the coating is generally equivalent to the surface area of the medical device upon which the coating is disposed. Thus, the surface area of the medical device surface limits the exposed surface area of the coating.
One way to increase the exposed surface area of the coating is to remove material from the surface of the medical device to increase the surface area upon which a coating can be disposed. However, removing material from the medical device can adversely impact the structural integrity of the medical device. For example, if holes are created in the struts of a stent, the structural integrity of the stent struts can be compromised causing the struts to become weak. Weak struts could result in the stent failing to expand properly or, once implanted, collapsing, potentially causing re-occlusion of a body lumen.
Accordingly, there is a need for a medical device having a coating with an increased exposed surface area for delivering a therapeutic agent to body tissue. Furthermore, there is a need for methods of making such medical device coatings having increased exposed surface area that do not adversely affect the structural integrity of the medical device